This invention relates to arc electrodes.
Arc electrodes have heretofore been made by using, as materials therefor, carbon or metals such as tungsten, iron, copper and nickel. When a DC potential is applied between electrodes formed of bars of such a material, the impulsion of ions which immediately ensues elevates the temperature of the cathode and consequently accelerates the discharge of thermal electrons, with the result that the arc discharge is continuous and takes place at a relatively low temperature. The arc lamp which utilizes the phenomenon of this arc discharge has advantages such as high luminous intensity, low brightness temperature and high electric power efficiency. Thus, it finds extensive utility in cine-projectors, photographic illuminators, flood lights, etc.
The conventional arc electrodes, when used in the atmosphere, provide neither fully satisfactory luminous intensity nor spectral distribution approximating that of white light. When they are used in the air, they are deficient in stability and the high-temperature zones of the electrodes undergo heavy oxidative corrosion and cause oxides of low electroconductivity to deposit on the surface thereof.
A primary object of this invention is to provide arc electrodes which give sufficient luminous intensity and produce spectral distribution approximating that of white light even in the atmosphere.
Another object of this invention is to provide arc electrodes which are stable in the air and which involve no appreciable oxidative corrosion.